Field of the Invention
The present invention relates to an organic light emitting display device, and more particularly, to a top emission type organic light emitting display device and a method of manufacturing the same.
Discussion of the Related Art
Organic light emitting display devices are self-emitting devices and have low power consumption, a fast response time, high emission efficiency, high luminance, and a wide viewing angle.
The organic light emitting display devices are classified into a top emission type and a bottom emission type, based on a transmission direction of light emitted from an organic light emitting device. In the bottom emission type, a circuit element is disposed between an emission layer and an image displaying surface, and for this reason, an aperture ratio is lowered. On the other hand, in the top emission type, the circuit element is not disposed between the emission layer and the image displaying surface, and thus, an aperture ratio is enhanced.
FIG. 1 is a schematic cross-sectional view of a related art top emission type organic light emitting display device.
As seen in FIG. 1, a thin film transistor (TFT) layer T which includes an active layer 11, a gate insulation layer 12, a gate electrode 13, an interlayer dielectric 14, a source electrode 15, and a drain electrode 16 is formed in an active area AA on a substrate 10, and a passivation layer 20 and a planarization layer 30 are sequentially formed on the TFT layer T.
An anode electrode 40 and an auxiliary electrode 50 are formed on the planarization layer 30. The auxiliary electrode 50 decreases a resistance of a cathode electrode 80 to be described below.
A bank 60 is formed on the anode electrode 40 and the auxiliary electrode 50 and defines a pixel area. An organic emission layer 70 is formed in the pixel area defined by the bank 60, and the cathode electrode 80 is formed on the organic emission layer 70.
In the top emission type, light emitted from the organic emission layer 70 travels through the cathode electrode 80. Therefore, the cathode electrode 80 is formed of a transparent conductive material, and for this reason, a resistance of the cathode electrode 80 increases. In order to decrease the resistance of the cathode electrode 80, the cathode electrode 80 is connected to the auxiliary electrode 50.
The gate insulation layer 12 and the interlayer dielectric 14 are formed in a pad area PA on the substrate 10, a signal pad 90 is formed on the interlayer dielectric 14, and the passivation layer 20 is formed on the signal pad 90. A hole is formed in the passivation layer 20, and the signal pad 90 is exposed to the outside through the hole. Since the signal pad 90 should be connected to an external driving circuit, the hole is formed in the passivation layer 20, and the signal pad 90 is exposed to the outside through the hole.
The related art top emission type organic light emitting display device has at least the following problems.
Since the signal pad 90 should be connected to the external driving circuit, a top of the signal pad 90 is exposed to the outside. For this reason, the top of the signal pad 90 is corroded, and the corrosion is spread to another area. In order to prevent the top of the signal pad 90 from being corroded, a metal layer which is good in corrosion resistance may be further formed on the top of the signal pad 90, but in this case, a separate process is additionally performed. Also, in order to prevent the top of the signal pad 90 from being corroded without the separate process being additionally performed, an electrode layer which is the same as the anode electrode 40 may be formed on the signal pad 90 through the same process, but in this case, it is unable to prevent corrosion from being made through a side of the electrode layer.
Moreover, in order to connect the signal pad 90 to the external driving circuit, the hole is formed in the passivation layer 20, and the top of the signal pad 90 is exposed through the hole. However, if the hole is previously formed in the passivation layer 20, an etchant for forming a pattern of the anode electrode 40 flows in through the hole to damage the signal pad 90. In order to prevent the damage, the hole of the passivation layer 20 for exposing the top of the signal pad 90 may be separately performed after a process of forming the pattern of the anode electrode 40 is completed, but in this case, a separate mask process is additionally performed.